Refrigeration



May 5, 1942,: c. c. cooNs ET AL.

REFRIGERATION Filed Nov. 25, 1938 ATTORNEY Patented May 5, 1942 UNITED STATES PATENT OFFICE REFRIGERATION Ohio Application November 25, 1938, Serial No. 242,220

17 Claims.

This invention relates to the art of absorption refrigeration and more particularly to a novel evaporator construction for such system.

In our co-pending application, Serial No. 386,395, filed April 2, 1941, which is a continuation-in-part of our application Serial No. 220,189, filed July 20, 1938, there is disclosed a refrigerating system including an evaporator in which the liquid refrigerant is supplied to the bottom portion of the evaporator and is conveyed upwardly therethrough as it is evaporating under the influence of a propelled relatively high velocity inert gas stream. While this evaporator construction is entirely satisfactory, the height of the evaporator is definitely limited by the allowable pressure drop in the inert gas stream between the inlet and outlet portions of the evaporator. be desirable to construct an evaporator having an unusually great height or to so arrange the system that an unusually large portion of the pressure differential created by the circulating fan is utilized for circulating the inert gas against the resistance interposed by the gas heat exchanger and absorber whereby only a relatively low pressure differential can be utilized in the evaporator for propelling the liquid refrigerant therethrough. This would limit the height of the evaporator if the designer were forced to rely upon the propelling action of the inert gas stream for elevating the liquid refrigerant entirely through all portions thereof.

Accordingly, it is an object of the present invention to provide an absorption refrigerating system of the above referred to typeincluding an evaporator so constructed and arranged that the height of the evaporator and the circulation of the refrigerant liquid are not directly dependent upon the allowable pressure drop in the inert gas stream between the gas inlet and outlet portions thereof.

It is a further object of this invention to provide an absorption refrigerating'system of the type including an evaporator in which the liquid refrigerant is propelled therethrough by an inert In some refrigerating systems it may,

gas stream in which there is provided a gas lift liquid refrigerant is elevated through the remaining evaporator height by means of a separate gas operated pump connected to the gas circulating system.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawing, in which the single figure of the drawing is a diagrammatic representation of an absorption refrigerating system embodying the invention and in which the evaporator is shown on an enlarged scale and in perspective.

Referring now to the drawing in detail, there is disclosed a three-fluid absorption refrigerating system comprising a boiler B, an analyzer D, an air-cooled rectifier R, a tubular air-cooled vertically positioned condenser C, an evaporator E, a gas heat exchanger H, a tubular air-cooled absorber A, a solution reservoir S, a liquid heat exchanger L, and a circulating fan F which is driven by an electrical motor M. The above described elements are interconnected by various conduits to form a plurality of gas and liquid circuits constituting a complete refrigerating system to which reference will be made in more detail hereinafter.

The refrigerating system will be charged with a suitable refrigerant, such as ammonia, a suitable absorbent, such as water, and a suitable inert pressure equalizing medium, such as nitrogen.

The boiler B will be heated in any suitable manner as by an electrical cartridge heater or by a gas burner as may be desired. The circulating motor M and the heater for the boiler B may be controlled in any suitable or desired manner. A preferred control mechanism is disclosed in U. S. Patent to Curtis C. Coons, Patent No. 2,228,343, dated January 14, 1941.

The application of heat to the boiler B generates refrigerant vapor from the strong solution normally contained therein. The refrigerant vapor so generated passes upwardly through the analyzer D in counterfiow to strong solution flowing downwardly therethrough. In the analyzer, vapor of absorption solution generated in the boiler is condensed by contact with the strong solution and the heat of condensation serves to generate further refrigerant vapor which then passes through the conduit II to the upper portion of a tubular air-cooled condenser C. The conduit I I includes the rectifier R which serves to cause condensation of any vapor of absorption solution which may pass through the analyzer D.

The refrigerant vapor discharges into the condenser C which extends to a level appreciably below the level of the top portion of the evaporator E and flows downwardly therethrough as it is being condensed by heat exchange with cooling air flowing over the outer surface of the condenser and the fins attached thereto. The condensate formed in the condenser C is then drained therefrom through a conduit l2, which includes a Ushaped liquid seal portion, into the bottom portion of the evaporator E to which reference will be made in more detail hereinafter. i

The weak solution formed in the boiler 13 b the generation of refrigerant vapor is conveyed therefrom through a conduit It, the outer path of the liquid heat exchanger L and a finned air-cooled conduit It to the lean solution reservoir S. The lean solution is drained from the bottom portion of the reservoir S into a gas lift pump conduit H which discharges into the upper portion of a tubular inclined air-cooled absorber A. It is apparent that the upper portion of the absorber is at an elevation above the liquid level normally prevailing in the boileri analyzer system wherefore some means must be provided to elevate the weak solution thereinto. For this purpose a small bleed conduit is is connected between the gas discharge conduit IQ of the circulating fan F and the gas lift pump conduit l'i below the liquid level normally prevailing therein, whereby the weak solution is elevated into the absorber by gas lift action.

The weal; solution flows downwardly through the asborber in counterfiow relationship to a rich mixture of pressure equalizing medium and refrigerant vapor which i conveyed thereto in a manner to be described more fully hereinafter.

In the absorber the refrigerant vapor content of the mixture is absorbed by the solution which then becomes strong solution and flows to the bottom portion of the absorber from which it is conveyed into the upper portion of the analyzer D by a conduit 2!, the inner path of the liquid heat exchanger L and a conduit 22.

The heat of absorption generated by the absorption process is subjected to air flowing over the outer Walls of the absorber vessel and in contact with the air-cooling fins mounted thereon.

The lean inert gas formed in the absorber is w conveyed from the upper end thereof through a conduit it into the suction inlet of' the circulating fan F in which it is placed under pressure and is discharged through the conduit i9 into the outer path .of the gas heat exchanger H. The lean inert gas is discharged from the outer path of the gas heat exchanger I-I through a conduit 25 into the bottom portion of the evaporator E.

The exact construction and operation'of the evaporator will be described more fully hereinafter, but for the present it is sufficient to note that the inert gas stream circulates upwardly through the evaporator in contact with'the liquid refrigerant which evaporates thereinto to produce refrigeration. The rich mixture formed in the evaporator is conveyed from the box-cooling conduit 26 thereof by means of a conduit 21 into the inner path of the gas heat exchanger H from which it is conveyed by a conduit 38 to the'bottom portion of the absorber A.

In the absorber A the rich mixture flows upwardly in counterflow to the absorption solution flowing'do-wnwardly therethrough in'the manner p viously described.

It will be noted that the weak solution reservoir S is vented to the suction side of the fan by means of a conduit 3| and that the condenser discharge conduit i2 is vented to the inner path of the gas heat exchanger H by means of a conduit 32. This construction places substantially the entire solution circuit under the suction pressure of the circulating fan F thereby tending to stabilize and improve operating conditions in all portions of the apparatus. This system is fully disclosed and claimed in the copending application of Curtis C. Coon and Rudolph S. Nelson,

Referring now to the evaporator E in detail,

' the same comprises a plurality of horizontal vertically spaced superposed coil sections 35, 3t and Sill. The coil sections 35 and 355 each comprise a pair of rearwardly facing U-shaped conduit sections which are designated 48 and 45 on the left and right-hand sides of the drawing, respectively. The outer legs of the coil sections 4!) and M are joined by rear cross-connecting conduits 43. The coil section 3i is identical with the coil sections 35 and '36 except that the inner leg of the conduit element ll is replaced by an L- shaped conduit it which opens into the forward portion of the large diameter rearwardly extending box-cooling conduit 26. The coil sections 35, and-3B are serially connected by a riser conduit 25, and the coil sections 36 and 31 are serially connected b-y-a riser conduit 41. The inert gas supply conduit 25 opens into the inner leg of the conduit section M] of the coil section 35.

The liquid refrigerant supply conduit 12 opens into the inert gas supply conduit 25 adjacent its point of connection withthe conduit section 40. The coil section 35h; provided with a drain conduit 4!? which opens into the upper portionof the coil section 4| adjacent its point of connection with the riser conduit 15 and communicates with the strong solution return line 2!.

The riser conduit 41 interconnecting the coil sections/38 andt'i is shunted by means of a gas lift pump conduit 53 which includes a U-shaped portion iii extending "below the level of the coil section 36. A gas supply conduit 52 is connected between the inert gas supply conduit 25 and the pumping conduit 5!] slightly below the level of the coil section 36 whereby liquid refrigerant may be elevated from the coil section 36' into the coil section 3'! by gas lift action.

It will be understood that the refrigerating system will be encased in a suitablecabinet with the mechanism properly distributed in lower and rear mechanism compartments and with the evaporator projecting into the storage compartment of the cabinet. The evaporator may be encased in a suitable housing including shelves resting'upo'ri the various coil sections 35 and 36 to support ice cube trays.

The evaporator including the conduit 25 may, if desired, be constructed of a single piece of relatively small diameter tubing, on the order of inside diameter, for example, or it may be constructed of suitablyshaped sections of tubing welded together as may be desired.

The operation of the invention is as follows: The liquid refrigerant which issupplied to the coil section 35 through the conduit i2 is propelled therethrough by the relatively high velocity stream of inert gas circulating through the evaporator. This refrigerant is elevated through theconduit 56 and-is also'circulated through the coil section' 36 by theinert'gas stream; however,

the liquid refrigerant is not elevated through the conduit 4! by the inert gas stream as the same drains from the coil section 36 into the U-shaped portion 5| of the gas lift pump 50 through which it is elevated by as lift action into the gas inlet portion of the coil section 31 through which it is again circulated by the propelling action of the inert gas stream and is then lifted upwardly through the conduit 45 into the box-cooling conduit 26. The liquid refrigerant flows through the box-cooling conduit 28 by gravity as the inert gas is flowing therethrough at too low a velocity to exert any propelling action thereon.

The drain 49 functions primarily as an emergency drain, as it is not normally operated for any purpose. During normal operation of the apparatus there is never a sufficient collection of liquid refrigerant in the coil section 35 to raise the level therein to the lowest portion of the drain 49. Any liquid collected therein is swept upwardly into the superposed coil section 35. However, if the apparatus should be up-ended, for example in shipping and installation, absorption solution might find its way into the coil section 35 and might block the same to inert gas flow were it not for the drain 49 which prevents this without completely draining the coil section 35. After a short period of operation of the refrigerator any liquid, such as absorption solution, which was trapped in the coil section 35 would be swept through the evaporator and eventually find its way into the absorption solution circuit. Also, during normal operation, the apparatus is preferably controlled intermittently as a result of which an appreciable quantity of liquid refrigerant flows downwardly into the coil section 35 when the circulating fan F is de-energized. With the arrangement illustrated, this liquid simply is stored in the evaporator and awaits re-energization of the apparatus to produce refrigeration, whereas if the drain 49 opened directly into the bottom portion of the coil 35, this liquid refrigerant would be wasted.

The action of the inert gas on the liquid refrigerant is as follows: In substantially horizontal and slightly inclined conduits the gas stream passes over the surface of a small stream of the liquid which it propels through the conduit by the dragging or frictional action exerted on the liquid b the gas. In rising and steeply inclined conduits the action is somewhat different, the liquid refrigerant collects to some extent and is maintained in a state of continual violent agitation by the continual discharge of inert gas therethrough, which inert gas blows, sweeps or drags a portion of the collected liquid into the next higher evaporator conduit Where the gas again propels the liquid in a stream as mentioned above.

The propelling action of the inert gas is a function of its density, pressure and velocity of flow. In a refrigerating system in which the total pressure ranges between 270. and 400 pounds per square inch, a dense inert gas, like nitrogen, will circulate the liquid refrigerant satisfactorily through an evaporator approximately or 11" in height constructed of tubing of approximately /2" inside diameter with a pressure drop of between 2%;" and 4 of Water between the gas inlet and outlet connections to the evaporator. Of course, these dimensions are all mutually inter-dependent and a variation in any one will require appropriate variation of the others in order to produce proper results. These dimensions are given by way of example only and are not to be construed as limiting in any sense. A full explanation of this phenomena will be found in our co-pending application, Serial No, 386,395, filed April 2, 1941, which is a continuation-inpart of our application Serial No. 220,189, filed July 20, 1938.

The figures given above have been found to be satisfactory for domestic refrigerating systems. However, it is not desirable to increase the size of the circulating fan, nor is it practical to increase the speed thereof, wherefore if a system be designed in which the'resistance to gas exchange in the absorber circuit is increased, this must be accomplished at the expense of available pressure drop in the evaporator with the result that the evaporator must either be decreased in height or some means must be provided to decrease the gas flow resistance thereof without materially interfering with the propelling action of the inert gas on the liquid refrigerant. Also, it may be desirable to provide an evaporator of an extraordinarily large height without increasing the pressure drop in the inert gas stream between the gas inlet and outlet portions thereof.

The present invention admirably solves these difiiculties in the following manner: The resistance to the inert gas stream interposed by the evaporator occurs principally in the riser conduits 46 and 41. This is apparently due to the fact that the liquid refrigerant is carried through the horizontal and slightly inclined conduits in the form of a small stream flowing along the bottom of the conduit over which the inert gas stream is passing as the stream evaporates and as it is being propelled along the conduit by the frictional drag exerted by the gas stream. However, in rising and steeply inclined conduits the action is somewhat different. In conduits of this character the inert gas stream maintains a violently agitated body of the liquid refrigerant through which the gas stream continuously blows or blasts its way and carries a portion of the body of liquid upwardly into the next horizontal coil section. The greatest resistance to the inert gas flow occurs in the substantially vertical sections of the evaporator in which the inert gas stream is maintaining an appreciable quantity of liquid in a state of continual violent agitation. Therefore, by eliminating one or more of the bodies of liquid so supported, the available height of the evaporator may be increased or the allowable pressure drop between the gas inlet and outlet portions of the evaporator may be decreased. According to the present invention this is accomplished by arranging the evaporator in such fashion that only inert gas traverses the intermediate lift 41 and the liquid refrigerant is elevated from thecoil section 36 into the coil section 31 by means of a gas lift pump 50.

The gas lift pump uses only a Very small quantity of gas and operates under pressure differentials existing between the conduit 25 and the conduit 41.

Though the evaporator and the interstage conveying mechanism has been illustrated herein in considerable detail, various modifications of this structure are contemplated within the scope of the invention. For example, a plurality of gas lift pumps might be utilized to convey the liquid refrigerant between various sections of the evaporator. Portions of the evaporator coils may be connected by gas lift pumps other than the ones so connected in the drawing. Though it is desirable to supply the inert gas from the evaporator inert gas inlet conduit because of the short direct connections thus permitted, the gas to operate the interstage gas lift pump or pumps may be supplied directly from the discharge of the circulating fan if the pressure drop between the circulating fan and the evaporator is such that gas at proper pressures are not available in the evaporator.

According to the present invention there is provided a simple evaporator construction which permits a high evaporator to be utilized without increasing the fan size to prohibitive dimension or to maintain a given evaporator size while decreasing the inertlgas pressure drop'therethrough, thereby allowing greater freedom in design of the absorber, gas heat exchanger, and other portions of the refrigerating system as a whole.

While the invention has been illustrated and described herein in considerable detail, it is not to be limited thereto but various changes may be made in the construction, arrangement, and proequalizing medium in different portions of said 1- unit for conveying cooling medium from one level to another therein.

2. Refrigerating apparatus comprising an upright evaporator, means for supplying refrigerant liquid to the lower portion of said evaporator, means for propelling a dense inert gas through said evaporator to circulate liquid refrigerant therethrough, and means for draining liquid refrigerant from an intermediate portion of said evaporator and for elevating such drained liquid refrigerant to a higher portion of said evaporator out of contact with the stream of inert gas flowing therethrough.

3. Refrigerating apparatus comprising an evaporator having portions at different elevations, means for supplying refrigerant liquid to the bottom portion of said evaporator, means for propelling a dense inertgas through said evaporator to circulate liquid refrigerant therethrough, and means for elevating liquid from one portion of said evaporator to a higher portion thereof by gas lift action.

4. Refrigerating apparatus comprising an evaporator having portions at different elevations, means for supplying refrigerant liquid to the bottom portion of said evaporator, means for propelling a dense inert gas through said evaporator to circulate liquid refrigerant therethrough, means for elevating liquid from one portion of said evaporator to a higher portion thereof by gas lift action, and means for bleeding inert gas from the stream entering said evaporator into said means for elevating liquid refrigerant by gas lift action.

5. Absorption refrigerating apparatus comprising an inert gas circuit including an evaporator having portions at different elevations and an absorber, a solution circuit including said absorber and a boiler, means for supplying refrigerant vapor generated in said boiler to the bottom portion of said'evaporator in liquid phase, power driven means for propelling a dense inert gas through said gas circuit in a direction such that it flows upwardly through said evaporator with a velocity sufiicient to sweep or drag liquid refrigerant through at least a portion of said evaporator, and means for withdrawing liquid refrigerant traveling through said evaporator from one portion of said evaporator and for elevating the liquid to another higher portion thereof independently of the inert gas which propelled the liquid to the point of withdrawal.

6. Refrigerating apparatus comprising a vertically extending evaporator, means for supplying refrigerant liquid to the lower portion of said evaporator, means for propelling an inert gas through said evaporator under conditions such that it will sweep or drag liquid refrigerant upwardly therethrough, and means for removing liquid refrigerant from an intermediate portion of said evaporator and raising it to a higher portion thereof out of contact with the inert gas stream flowing through said evaporator.

'7. Refrigerating apparatus comprising an upstanding evaporator, means for supplying a liquid refrigerant to the lower portion of said evaporator, means for propelling an inert gas through said evaporator under conditions such that it will sweep or drag liquid refrigerant upwardly x therethrough as it is evaporating to produce refrigeration, a gas lift pump interconnecting intermediate portions of said evaporator, and means for bleeding inert gas from another portion of the system to operate said gas lift pump to relieve the inert gas flowing through said evaporator of the burden of lifting liquid refrigerant between the elevations interconnected by said gas lift pump.

' 8. Absorption refrigerating apparatus comprising an evaporator including a plurality of vertically spaced coil sections, rising conduits serially connecting adjacent coil sections, means for supplying liquid refrigerant to the bottom portion of said evaporator, means for propelling an inert gas through said evaporator under conditions such that it will circulate liquid refrigerant upwardly therethrough, gas lift pump means interconnecting two of said coil sections of said evaporator, and means for supplying inert gas to operate said pump.

9. Refrigerating apparatus comprising an upstanding evaporator, means for supplying liquid refrigerant to the lower portion of said evaporator, means for circulating a pressure equalizing medium upwardly through said evaporator under conditions such that it will convey the liquid refrigerant therethrough, and means for removing liquid refrigerant from an intermediate portion of said evaporator and for returning it to another higher portion thereof to relieve the pressure equalizing medium of the resistance of the liquid in a portion of its path of flow through the evaporator.

l0. Refrigerating apparatus comprising an upstanding evaporator, means for supplying liquid refrigerant to the bottom of said evaporator, means for circulating a pressure equalizing medium through a circuit including said evaporator with sufficient force to sweep or drag the liquid refrigerant upwardly through a portion of said evaporator, and means for removing liquid being circulated by the pressure equalizing medium from one portion of said evaporator and for returning the liquid to another higher portion of said evaporator to insure that the'liquid refrigerant will be supplied to all portions of said evaporator.

11. Refrigerating apparatus comprising a vertically extending evaporator, means for supplying liquid refrigerant to the lower portion of said evaporator, means for circulating a pressure equalizing medium through a circuit including said evaporator with a velocity sufficient to exert a propelling force on the liquid refrigerant in said evaporator, said evaporator being so constructed and arranged that the pressure equalizing medium will circulate refrigerant through only a portion thereof, gas lift pumping means for conveying liquid refrigerant between two separated parts of the evaporator to relieve the propelling load on the pressure equalizing medium and means for bleeding pressure equalizing medium from a portion of said circuit to operate said pumping means.

12. Refrigerating apparatus comprising a vertically extending evaporator, means for supplying liquid refrigerant to the bottom of said evaporator, means for circulating a pressure equalizing medium through said evaporator with sufficient force to propel liquid refrigerant upwardly through only a portion of the total height thereof, gas lift pumping means constructed and arranged to elevate liquid from one-elevation of said evaporator to a higher elevation therein, and means for supplying pressure equalizing medium to operate said pumping means.

13. Absorption refrigerating apparatus including an elongated evaporator conduit having sections at different elevations connected by rising sections, means for supplying a liquid refrigerant to the bottom portion of said conduit, means for propelling a pressure equalizing medium upwardly through said conduit with a velocity sufficient to propel liquid refrigerant through a portion of said conduit, and means for withdrawing liquid refrigerant from said conduit at one level and for returning such liquid to said conduit at a higher level to reduce the lifting load on the pressure equalizing medium flowing through said conduit.

14. Absorption refrigerating apparatus including an elongated evaporator conduit having sections at different elevations connected by rising sections, means for supplying a liquid refrigerant to the bottom portion of said conduit, means for propelling a pressure equalizing medium upwardly through said conduit with a velocity sufficient to propel liquid refrigerant through a portion of said conduit, a gas lift pump conduit to receive liquid refrigerant from said conduit at one level and to return such liquid refrigerant to said conduit at a higher level, and means for diverting pumpingpressure equalizing medium to said pump from the stream of pressure equalizing medium flowing to said evaporator and prior to contact of such pressure equalizing medium with liquid refrigerant.

l5. Refrigerating apparatus comprising an upstanding cooling unit, means for supplying a cool-- ing medium in liquid form to the lower portion of said cooling unit, means for circulating a pressure equalizing medium upwardly in said unit in surface contact with a body of said liquid refrigerant and with sufiicient force to convey liquid therewith, and pumping means for conveying cooling medium between spaced apart points on said cooling unit.

16. Absorption refrigerating apparatus comprising an upstanding evaporator, an absorber, a refrigerant liquefying means connected to supply liquid refrigerant to the lower portion of said evaporator, a generator connected to supply refrigerant vapor to said liquefying means, means connecting said evaporator and absorber for circulation of an inert gas therebetween including means for circulating the inert gas upwardly through at least a portion of said evaporator with sufiicient pressure and velocity to propel the refrigerant liquid and to elevate such liquid through at least a portion of said evaporator, and pumping means connected to withdraw refrigerant liquid from said evaporator at one level and to return such refrigerant liquid to said evaporator at a higher level.

17. An evaporator adapted for use in an absorption refrigeration apparatus of the type in which liquid refrigerant evaporates into an inert medium in gaseous phase comprising an upstanding cooling unit having an upwardly extending fluid passageway therethrough, means for supplying a cooling medium to a lower portion of said passageway, means for circulating a pressure equalizing medium upwardly through said passageway with sufficient velocity and pressure to elevate the cooling medium through at least a portion of said passageway, and means operated by the pressure difi'erential of said pressure equalizing medium prevailing at spaced apart points in said fluid passageway for conveying cooling medium from one portion to another portion of said fluid passageway.

CURTIS C. COONS. WILLIAM H. KI'ITO. 

